Dosimetrically motivated beam-angle optimization for non-coplanar arc radiotherapy with and without dynamic...

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Non-coplanar radiotherapy techniques enhance dose distribution over coplanar methods.
• Optimizing beam directions for non-coplanar techniques remains a challenge.
• Dynamic collimator trajectory radiotherapy (colli-DTRT) utilizes non-coplanar partial arcs and dynamic collimator rotation.

Purpose of the Study:

• To address the beam angle optimization (BAO) problem for colli-DTRT and non-coplanar VMAT (NC-VMAT).
• To determine optimal table-angle and gantry-angle ranges for partial arcs.
• Achieved through iterative 4π fluence map optimization (FMO) and beam direction elimination.

Main Methods:

• BAO evaluates all beam directions on a gantry-table map.
• FMO scores beam contributions, followed by thresholding to eliminate suboptimal directions.
• Iterative FMO and arc candidate trimming refine the gantry angle range, followed by direct aperture optimization.

Main Results:

• colli-DTRT and NC-VMAT showed improved dosimetric performance versus coplanar VMAT for most sites, except prostate.
• Mean dose reductions to parallel organs were observed, with specific reductions in D2% for serial organs.
• Delivery times were under 4 minutes, comparable to class-solution methods, though optimization time increased.

Conclusions:

• Successfully developed dosimetrically motivated BAO for colli-DTRT and NC-VMAT.
• colli-DTRT and NC-VMAT are applicable to diverse treatment sites.
• These techniques offer beneficial or equivalent dosimetric performance with acceptable delivery times.